I have seen quite a few questions on the subject of how to determine ring size for scope mounting so thought I'd share this easy method. Its just arithmetic, not calculus. Hope this helps someone.

1. Measure outside diameter of the front Objective.
2. Divide the measurement by 2.
3. For a 1” diameter tube subtract 1/2”
4. Add 1/8” for barrel clearance, 1/4” if you will install lens covers.
5. You now have the height that you need from the top of the scope mount or dovetail to the saddle of the rings.
6. Most if not all scope ring manufacturers provide these dimensions on their WebSite.

4a. Add 1/4” for barrel clearance and lens cover = 3/4” (Height of rings from top of scope mount or dovetail to the saddle of the rings.)

5. If a Weaver/Pictanny type scope rail is used, measure the height of the rail above the barrel and subtract that from the scope ring height determined in step 4 or 4a.

For scopes that have different size tubes such as 30mm, measure the tube diameter in inches and divide by 2. Substitute that value for the value in step 3 of the example.

A final note. For some scopes the size of the Ocular (rear eye piece) can interfere with the cycling of the bolt on some bolt action rifles. CZ rifles have a fairly high bolt throw so beware of this issue on a scope that has a large Ocular.